## Impedance Relay

Distance Relays are of three types: ·         Impedance Relay ·         Reactance Relay ·         MHO Relay. Impedance Relay: As from Universal Relay Torque Equation, T = K1I2+K2V2+K3VICos(Ɵ-Ƭ)+K4 Where K1 = Constant             K2 = Constant             K3 = Constant             K4 = Spring Torque             V = Voltage fed to the Relay             I = Current … Read more Impedance Relay

## Directional Earth Fault Protection

Generally earth faults are Single Line to Ground (SLG) and Line-Line to Ground (LLG) faults. Earth faults are characterized by the presence of Zero Sequence Curren I0. Since, except for unbalance, normal system operation is not having Zero Sequence Current I0, much more sensitive pick-up is possible for earth fault by using zero sequence current … Read more Directional Earth Fault Protection

## How Directional Feature Incorporated in a Relay?

Why Directional Relay? For understanding the need of Directional Relay we consider a power system as shown in figure below. For fault at F1, Relay R2 is supposed to pick-up and operate the circuit breaker. Similarly for fault at F2, Relay R1 shall operate to isolate the faulty section from the healthy section. Now suppose … Read more How Directional Feature Incorporated in a Relay?

## Over Current Relay and Its Characteristics

Protection schemes can be divided into two major groups: a) Unit schemes, and b) Non-unit schemes. a) Unit Scheme: Unit type schemes protect a specific area of the system i.e. a transformer, transmission line, generator or bus bar.The unit protection schemes are based on Kirchhoff’s Current Law – the sum of the currents entering an … Read more Over Current Relay and Its Characteristics

## Measurement of Medium Resistance by Substitution Method

In Substitution Method, the Resistance whose value is to be measured is compared with the Standard Resistance by some technique which is described in this section. The connection diagram for Substitution Method is given below. Here, R is the unknown Resistance, S the Standard variable Resistance, A is Ammeter and r is Regulating Resistance. When … Read more Measurement of Medium Resistance by Substitution Method

## Voltmeter Ammeter Method for Measurement of Resistance

Resistance is classified into three categories for the sake of Measurement. Different categories of Resistance are measured by different technique. That’s why they are classified. They are classified as Low Resistance:  Resistance having value 1Ω or below are kept under this category. Medium Resistance: This category includes Resistance from 1Ω to 0.1 MΩ. High Resistance: … Read more Voltmeter Ammeter Method for Measurement of Resistance

## Resistance

It is impossible to make a perfect / ideal circuit component which can have only one property. For example a Resistor do not have only resistance rather it have associated inductance and Capacitance too. Same is the case with Capacitor and Inductor. Therefore a circuit component have some impurity which causes unwanted quantities in the circuit known … Read more Resistance

## Schering Bridge – Measurement of Capacitance and Dissipation Factor

We will discuss how to measure Capacitance and Dissipation Factor. Capacitance is measured by using Schering Bridge. What is this Schering Bridge? First we will discuss how to balance a bridge.   As we know for balanced bridge, there should not be any current through the detector which means the potential difference across the detector … Read more Schering Bridge – Measurement of Capacitance and Dissipation Factor

## Capacitance and Dissipation Factor

A Capacitor is a device which has the capability to store energy in its Electric Field. Therefore we can say that a Capacitor can store charge. There are many types of Capacitor but the most basic Capacitor is Parallel Plate Capacitor. We will consider this basic capacitor for getting idea of basic but important parameters … Read more Capacitance and Dissipation Factor

## Dynamic Contact Resistance Measurement, DCRM

First question which strikes in our mind is that why do we need to do DCRM even though we already had Contact Resistance Measurement,CRM? Seems good question and this question will take you to the depth. So, first of all we need to know about the contacts of Circuit Breaker. Basically, a CB has two types … Read more Dynamic Contact Resistance Measurement, DCRM